Extraocular Muscles (EOMs)
Six muscles control eye movement, innervated by cranial nerves III, IV, and VI. A simple mnemonic to remember innervation is LR6(SO4)3:
| Muscle | Action | Innervation |
|---|---|---|
| Lateral Rectus | Abduction (moves eye laterally) | CN VI (Abducens) |
| Superior Oblique | Intorsion, depression, abduction | CN IV (Trochlear) |
| Superior Rectus | Elevation, intorsion, and adduction | CN III (Oculomotor) |
| Inferior Rectus | Depression, extorsion, adduction | CN III (Oculomotor) |
| Medial Rectus | Adduction (moves the eye medially) | CN III (Oculomotor) |
| Inferior Oblique | Extorsion, elevation, abduction | CN III (Oculomotor) |
High-Yield Testing Tip:
- To isolate the vertical muscles (Recti), abduct the eye first; to isolate the oblique muscles, adduct the eye first.
- CN IV Palsy: Patients present with vertical diplopia and often tilt their head away from the affected side to compensate.
- CN VI Palsy: The most common isolated CN palsy; results in medial strabismus (eye pulled inward).